Practice of Epidemiology Estimates of Nondisclosure of Cigarette Smoking Among Pregnant and Nonpregnant Women of Reproductive Age in the United States

Although clinic-based studies have used biochemical validation to estimate the percentage of pregnant women who deny smoking but are actually smokers, a population-based estimate of nondisclosure of smoking status in US pregnant women has not been calculated. The authors analyzed data from the 1999–2006 National Health and Nutrition Examination Survey and estimated the percentage of 994 pregnant and 3,203 nonpregnant women 20–44 years of age who did not report smoking but had serum cotinine levels that exceeded the defined cut point for active smoking (nondisclosure). Active smoking was defined as self-reporting smoking or having a serum cotinine concentration that exceeded the cut point for active smoking. Overall, 13.0% (95% confidence interval (CI): 8.8, 17.1) of pregnant women and 29.7% (95% CI: 27.3, 32.1) of nonpregnant women were active smokers. Nondisclosure was higher among pregnant active smokers (22.9%, 95% CI: 11.8, 34.6) than among nonpregnant smokers (9.2%, 95% CI: 7.1, 11.2). Among pregnant active smokers, nondisclosure was associated with younger age (20–24 years). Among nonpregnant active smokers, nondisclosure was associated with Mexican-American and non-Hispanic black race/ethnicity. Studies and surveillance systems that rely on self-reported smoking status are subject to underestimation of smoking prevalence, especially among pregnant women, and underreporting may vary by demographic characteristics.